Porous electrode

Abstract

The invention relates to a porous electrode at least containing a porous catalytic layer, which layer at least contains 3-30 parts by weight of mouldable polymeric binder, 50-94 parts by weight of carbon particles and 3-47 parts by weight of hard hydrophobic polymer particles.

We claim: 
     
       1. A porous electrode including a porous catalytic layer which comprises at least 3-30 parts by weight of moldable polymeric binder, 50-94 parts by weight of carbon particles, and 3-47 parts by weight of hard hydrophobic polymer particles. 
     
     
       2. A porous electrode according to claim 1, wherein a major portion of the moldable polymeric binder is polytetrafluoroethylene. 
     
     
       3. A porous electrode according to claim 2, wherein the moldable polymeric binder is at most 5% by weight amorphous polymer. 
     
     
       4. A porous electrode according to claim 1, wherein a major portion of the hard hydrophobic polymer is hard polytetrafluoroethylene. 
     
     
       5. A porous electrode according to claim 1, wherein a major portion of the hard hydrophobic polymer is hard tetrafluoroethylene-hexafluoropropylene-copolymer. 
     
     
       6. A porous electrode according to claim 1, wherein a major portion of the hard hydrophobic polymer consists of a mixture of hard polytetrafluoroethylene and hard tetrafluoroethylene-hexafluoropropylene-copolymer. 
     
     
       7. A porous electrode according to claim 1, wherein a major portion of the moldable polymeric binder is moldable polytetrafluoroethylene and a major portion of the hard hydrophobic polymer is hard polytetrafluoroethylene prepared from the same moldable polytetrafluoroethylene. 
     
     
       8. A porous electrode according to claim 1, wherein the hard hydrophobic polymer particles contain at least 10% (wt) amorphous polymer. 
     
     
       9. A porous electrode according to claim 1, wherein the hard hydrophobic polymer particles contain at most 60% (wt) amorphous polymer. 
     
     
       10. A porous electrode according to claim 1, wherein the hard hydrophobic polymer particles contain at most 50% (wt) amorphous polymer. 
     
     
       11. A porous electrode according to claim 1, wherein the hard hydrophobic polymer particles contain at most 40% (wt) amorphous polymer. 
     
     
       12. A porous electrode according to claim 1, wherein a major portion of the hydrophobic polymer is polytetrafluoroethylene that has been subjected, before being used in the production of the catalytic layer, to a heat treatment at 550-700 K. for 1s-5 hours. 
     
     
       13. A porous electrode according to claim 1, wherein a major portion the hydrophobic polymer is polytetrafluoroethylene that has been subjected, before being used in the production of the catalytic layer, to a heat treatment at 550-700 K. for 5s-2 hours. 
     
     
       14. A porous electrode according to claim 1, wherein a major portion of the hydrophobic polymer is polytetrafluoroethylene that has been subjected, before being used in the production of the catalytic layer, to a heat treatment at 600-650 K. for 5s-2 hours. 
     
     
       15. A porous electrode according to claim 1, further comprising a porous metal collector. 
     
     
       16. A porous electrode according to claim 1, wherein at least part of the carbon particles is provided with catalytically active noble metal. 
     
     
       17. A porous electrode according to claim 1, wherein at least part of the carbon particles is provided with catalytically active noble metal and the catalytically active noble metal is palladium and/or platinum. 
     
     
       18. A porous electrode according to claim 1, wherein 10-90% (wt) of the carbon particles is provided with catalytically active noble metal.